IC socket, a test method using the same and an IC socket mounting mechanism

ABSTRACT

An IC to be tested having solder bumps is mounted on an IC socket mounted on a test board. The IC socket is provided with a contact unit including a plurality of straight contact pins each having an lower end connected to the test board and an upper end connected to the solder bumps and also including an elastic member for supporting the plurality of contact pins. A diameter of the plurality of contact pins is configured to be sufficiently small for the plurality of contact pins to pierce the respective solder bumps so that an electrical connection is established by the upper end of each of the plurality of solder bumps piercing an associated one of the solder bumps.

This application is a division of prior application Ser. No. 08/820,357filed Mar. 12, 1997, now U.S. Pat. No. 6,229,320, which is acontinuation-in-part of application Ser. No. 08/531,449, filed Sep. 21,1995, now U.S. Pat. No. 5,854,558.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to IC sockets, test methods using the sameand IC socket mounting mechanisms, and more particularly, to an ICsocket for testing a semiconductor device (IC) having projectionelectrodes formed as bumps or the like, a test method using such an ICsocket and a mechanism for mounting such an IC socket.

Many of the ICs used recently are constructed to have projectionelectrodes formed as solder bumps for connection with an externaldevice, for the purpose of reducing the size of a package. For example,a ball grid array (BGA) has such a construction. Demands forhigh-density, high-speed semiconductor devices having projectionelectrodes are growing for further reduction in the package size.Associated with this, pitch between electrodes is on a decreasing trend;and projection electrodes are being arranged with an increasingly higherdensity and on an increasingly reduced scale.

Once produced, the ICs are subject to a performance test to see if aprescribed performance is provided. The ICs are tested by being mountedon an IC socket. Therefore, the IC socket should be adapted for thehigh-density, small-scale trend of the ICs. As a result of thehigh-density, small-scale trend, the strength of each projectionelectrode has become extremely low so that it is necessary to ensurethat the projection electrodes are not damaged when brought into contactwith contact pins provided in the IC socket.

2. Description of the Related Art

FIGS. 1-5 show a construction of a conventional IC socket 1. As shown inFIGS. 1-3, the IC socket 1 generally comprises a socket body 2, a lid 3,contact pins 4 and a substrate 5. The IC socket 1 is designed so that anIC 7 of a BGA type provided with solder bumps 6 (projection electrodes)is mounted on the IC socket 1 and tested for its performance.

The socket body 2 includes a cavity 8 in which the substrate 5 isfitted. The cavity 8 is provided with through holes 9 aligned with thesolder bumps 6 formed in the IC 7. The substrate 5 is provided withmounting holes 10 also aligned with the solder bumps 6 formed in the IC7.

The contact pins 4 are formed by punching a thin metal plate so as tohave a crooked configuration that provides a spring action as shown inFIGS. 2 and 3. The contact pins 4 have contact parts 4 a, formed at theupper end thereof, inserted into mounting holes 10 of the substrate 5.Terminal parts 4 b formed at the lower end the contact pins 4 areinserted into the through holes 9 formed in the cavity 8 and are made toproject from the bottom of the socket body 2. The same number of thecrooked contact pins 4 is provided as the number of solder bumps 6formed in the IC 7. The contact pins 4 are designed to remainpress-fitted into the through holes 9 and the mounting holes 10 whilebeing accommodated in the IC socket 1.

The lid 3 is rotatably fitted to the socket body 2 by a pivot part 11.By closing the lid 3 when the IC 7 has been mounted on the socket body2, the lid 3 presses the IC 7 toward the substrate 5. As a result, thebumps 6 formed in the IC 7 are pressed against the contact parts 4a ofthe contact pins 4. The contact pins 4 are elastically deformed so as topress the solder bumps 6 by the elastic action. Accordingly, the contactpins 4 and the solder bumps 6 are electrically connected. A lock lever12 is provided in a lid 3. The lock lever 12 locks the lid 3 in theclosed position.

The IC socket 1 having the above-described construction is designed tobe mounted on a test board 13 by a solder reflow process or the likeafter the terminal parts 4 b projecting from the underside of the socketbody 2 are inserted into through holes 14 formed in the test board 13.The test board 13 is connected to a test device (for example, a burn-intest device) for performing a test of the IC 7. Thus, a prescribed testis performed on the IC 7 mounted on the IC socket 1 via the test board13.

It is known that a thin oxide film 15 (see FIG. 5) is formed on thesurface of the solder bumps 6 formed in the IC 7. Since the oxide film15 has a low conductivity, it is necessary to penetrate the oxide film15 in order to establish an electrical connection between the solderbumps 6 and the contact pins 4.

Conventionally, as shown in FIG. 4 showing the part A indicated by thearrow in FIG. 3 on an enlarged scale, the elastic deformation of thecontact pins 4 occurring when the lid 3 is closed is utilized. Morespecifically, it is expected that the elastic deformation causes thecontact parts 4 a of the contact pins 4 to be displaced in the directionindicated by the arrow of FIG. 4 so that the contact parts 4 a slide onthe surface of the solder bumps 6 such that the contact parts 4apenetrate the oxide film 15.

With the increasingly smaller solder bumps 6 provided on the IC 7recently, the strength of the solder bumps 6 has decreased. Accordingly,the method whereby the contact parts 4 a are expected to penetrate theoxide film 15 by sliding on the surface of the solder bumps 6 produces adeformation in the solder bump 6 while the contact parts 4 a slide onthe surface thereof. The deformation of the solder bumps is indicated bythe arrow 6 a of FIG. 5. If any of the solder bumps 6 is deformed, avariation in the height of the solder bumps 6 occurs when the IC 7 ismounted on a circuit board or the like after the test. The solder bumps6 may not be properly mounted on the circuit board.

In the conventional IC socket 1, a high level of precision is requiredto provide the contact pins 4 having a crooked configuration thatprovides a spring action in the socket body 2. The press-fitting of thecrooked contact pins 4 demands intensive attention. Another problems isthat, as the size of the contact pins 4 become smaller with thereduction in the size of the solder bumps 6, it is increasinglydifficult to produce the contact pins 4 having a complex crookedconfiguration, and the cost of the production increases accordingly.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an ICsocket, a test method using the same and an IC socket mountingmechanism.

Another and more specific object of the present invention is to providean IC socket, capable of performing high-precision testing withoutdamaging small projection electrodes, a test method using such an ICsocket and an IC socket mounting mechanism for mounting such an ICsocket.

In order to attain the aforementioned. objects, the present inventionprovides an IC socket mounted on a test board while in use and having asemiconductor device with projection electrodes mounted on said ICsocket for testing, said IC socket is constructed such that a diameterof a plurality of straight contact pins having a first end electricallyconnected to said test board and a second end thereof connected to saidprojection electrodes is sufficiently small for each of said pluralityof contact pins to pierce said projection electrodes, said IC socketbeing electrically connected to said test board by said first end ofsaid plurality of contact pins piercing said projection electrodes.

According to the IC socket of the present invention described above, oneend of each of the contact pins constituting the contact unit iselectrically connected to a test board and the other end is connected tothe projection electrodes. Thus, an electrical connection is properlyestablished between the projection electrodes and the test board.

By configuring the diameter of the contact pin to be small enough forthe contact pin to pierce the projection electrode for an electricalconnection therewith, it is ensured that, even if an insulating filmsuch as an oxide film is created on the projection electrode, thecontact pin can be electrically connected to the projection electrode bypenetrating the insulating film.

Since the contact pin has a significantly small diameter, the projectionelectrode is not deformed, only a fine hole being created in theprojection electrode when pierced by the contact pin. Thus, ahigh-precision mounting of an IC is possible.

Even with its fine diameter, it is highly unlikely that the contact pinis bent or curved because the contact pins are supported by thesupporting structure constituting the contact unit. Therefore, anelectrical connection is properly established between the contact pinand the projection electrode.

The aforementioned objects may also be attained by an IC socket mountedon a test board while in use and having a semiconductor device withprojection electrodes mounted on said IC socket for testing, said ICsocket comprising: a plurality of straight contact pins having a firstend electrically connected to said test board and a second end connectedto said projection electrodes; and a supporting structure for supportingsaid plurality of contact pins, each of said plurality of contact pinsprovided at the second end with a deformable part deformable accordingto a pressure occurring between said contact pin and an associated oneof said projection electrodes.

According to the IC socket according to the present invention describedabove, deformation of the deformable part provided at that portion ofthe contact pin which is connected with the projection electrode cancelsa variation in the height of the projection electrodes or a variation inthe pressure caused by an irregularity on the surface of the test board.Since the deformable part is deformed in conformity to the configurationof the projection electrodes, a relatively large contact area issecured. Thus, the deformable part is suitable for improving anelectrical conductivity between the contact pins and the projectionelectrodes.

Even when the projection electrodes are formed of a soft metal such as asolder, the pressure applied to the projection electrodes is relativelysmall as a result of the deformable part being deformed. Accordingly, anelectrical connection can be properly established between the contactpins and the projection electrodes without causing damage in theprojection electrodes.

The aforementioned objects may also be attained by an IC socket mountingmechanism for mounting, on a test board, an IC socket comprising acontact unit having a plurality of straight contact pins forelectrically connecting the test board and projection electrodes of asemiconductor device and also having a supporting structure forsupporting said plurality of contact pins, the test board included insaid IC socket mounting mechanism being provided with through holes towhich said plurality of contact pins are electrically connected, andeach of said plurality of contact pins having one end thereof connectedto said test board and provided with an elastically deformable part sothat an elastic resilient force generated when said elasticallydeformable part is inserted in an associated one of said through holescauses said contact pin to be pressed against the through hole and toestablish an electrical connection therewith.

According to the IC socket mounting mechanism of the present invention,a relatively simple operation of inserting the elastically deformablepart into the through hole ensures that an electrical connection isestablished between the contact pins and the test board. Since theelastically deformable part in the through hole presses the through holeby an elastic resilient force, an improved electrical connection betweenthe contact pins and the test board is established.

The present invention also provides an IC socket mounting mechanism formounting, on a test board, an IC socket comprising a contact unit havinga plurality of straight contact pins for electrically connecting thetest board and projection electrodes of a semiconductor device and alsohaving a supporting structure for supporting the plurality of contactpins, the test board included in the IC socket mounting mechanism beingprovided with through holes at a pitch greater than a pitch at which theprojection electrodes are arranged, and each of the plurality of contactpins is configured to be long enough to extend from the supportingstructure to reach an associated one of the through holes formed in thetest board.

According to the IC socket mounting mechanism described above, thethrough holes can be arrayed at a relatively wide pitch even if thepitch at which the projection electrodes are arrayed is relativelysmall. Thus, forming of the through holes becomes easier, and forming ofthe wiring pattern provided on the test board for connection with thethrough holes also becomes easier.

The aforementioned may also be attained by an IC test system for testinga semiconductor device mounted on an IC socket which is mounted on atest board connected to a test device, the IC socket being constructedsuch that a diameter of a plurality of straight pins having a first endelectrically connected to the test board and a second end thereofconnected to the projection electrodes is sufficiently small for each ofthe plurality of contact pins to pierce the projection electrodes, theIC socket being electrically connected to the test board by the firstend of the plurality of contact pins piercing the projection electrodes.

The present invention further provides an IC test system for testing asemiconductor device mounted on an IC socket which is mounted on a testboard connected to a test device, said IC socket comprising: a pluralityof straight contact pins having a first end electrically connected tosaid test board and another end connected to said projection electrodes;and a supporting structure for supporting said plurality of contactpins, each of said plurality of contact pins provided at the second endwith a deformable part deformable according to a pressure occurringbetween said contact pin and an associated one of said projectionelectrodes.

According to the IC test system of the present invention, thereliability of the test on a semiconductor device can be improvedbecause an electrical connection between the projection electrodes ofthe semiconductor device and the contact pins of the IC socket can beproperly established.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a conventional IC socket;

FIG. 2 is an exploded perspective view of the conventional IC socket;

FIG. 3 is a sectional view of the conventional IC socket;

FIG. 4 is an enlarged view of a portion of FIG. 3;

FIG. 5 illustrates a problem with the conventional IC socket;

FIG. 6 shows a basic construction of an IC socket according to thepresent invention;

FIG. 7 is a schematic illustration of a construction of the IC socketaccording to a first embodiment of the present invention;

FIG. 8 is a partial enlarged view of the IC socket according to thefirst embodiment before an IC is mounted on the IC socket;

FIG. 9 is a partial enlarged view of the IC socket according to thefirst embodiment after the IC is mounted on the IC socket;

FIG. 10 is a schematic view of an IC socket according to a secondembodiment of the present invention;

FIG. 11 is an enlarged view of a part indicated by the arrow B of FIG.10;

FIG. 12 is an enlarged view of a part indicated by the arrow C of FIG.10;

FIG. 13A shows how an IC is positioned in the supporting structure;

FIG. 13B is a partial enlarged view of FIG. 13A;

FIG. 14A shows how an IC is positioned in the supporting structure;

FIG. 14B is a partial enlarged view of FIG. 14A;

FIG. 15 is a partial enlarged view of an IC socket according to a thirdembodiment of the present invention;

FIG. 16 is a bottom view of a guide plate provided in the IC socketaccording to the third embodiment;

FIG. 17 is a partial enlarged view of an IC socket according to a fourthembodiment of the present invention;

FIG. 18 is a partial enlarged view showing an operation of the IC socketaccording to the fourth embodiment of the present invention;

FIG. 19 is a partial enlarged view of an IC socket according to a fifthembodiment of the present invention;

FIGS. 20A-20C show configurations of an upper end of a contact pin;

FIGS. 21A and 21B show configurations of an upper end of a contact pin;

FIGS. 22A and 22B show configurations of an upper end of a contact pin;

FIGS. 23A-23C show configurations of an upper end of a contact pin;

FIGS. 24A-24C show variations of an IC socket mounting mechanism; and

FIG. 25 shows how a contact pin is connected to a test board.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 6 shows a basic construction of an IC socket 200 according to thepresent invention. Referring to FIG. 6, the IC socket 200 comprises asocket body 21, a lid 22 and contact pins 30. The IC socket 200accommodates a semiconductor device 25 (IC) of a BGA type provided withprojection electrodes 28 so as to test the IC 25.

While the description given below assumes that the projection electrodesare embodied by solder bumps, the present invention may be applied toother types of projection electrodes. More specifically, the presentinvention may be applied to ICs having wire bumps, bumps formed byplating, etc.

The socket body 21 is formed of a molded resin. A cavity 26 is formedinside the socket body 21. The contact pins 30 are arrayed in the cavity26.

The lid 22 is pivotably fitted to the socket body 21 by a pivot part 27.When the lid 22 is closed after the IC 25 is mounted on the socket body21, the lid 22 acts to press the IC 25 toward the contact pins 30.Accordingly, the solder bumps 28 formed in the IC 25 are pressed againstthe contact pins 30 so that the contact pins 30 are electricallyconnected to the solder bumps 28. The lid 22 is provided with a locklever 29 for causing the lid 22 to be locked in a closed position.

The IC socket 200 having the above described construction is mounted ona test board 32 connected to a test device (for example, a burn-in testdevice) for testing the IC 25. More specifically, IC socket 200 ismounted on the test board 32 such that the contact pins 30 projectingfrom the underside of the socket body 21 are pressed against land parts33 formed on the test board 32. Thus, the lower ends of the contact pins30 are electrically connected to the land parts 33. The IC socket 200may be secured to the test board 32 by an adhesive or by screws.

In the above-described construction, the contact pins 30 are embodied bymetal wires instead of being formed by punching a thin plate as is donein the conventional IC socket. Another point of note is that the contactpins 30 have a straight configuration instead of the conventionalcrooked configuration. Since the contact pins 30 are straight, thecontact pins 30 can be formed by cutting metal wires in a predeterminedlength. Since such a process does not require a die, the cost ofproduction can also be reduced.

It is necessary for the contact pins 30 to be harder than the solderbumps 28 formed in the IC 25 and to provide a certain spring action asdescribed later. The contact pins 30 may preferably be formed of atungsten that provides a good spring action or a beryllium copper havinga favorable electric characteristic.

The diameter (L1) of the contact pins is designed to be ⅕-{fraction(1/10)} of the diameter (L2) of the solder bumps 28 (projectionelectrodes) (L1/L2=⅕-{fraction (1/10)}). More specifically, when thediameter L2 of the solder bumps 28 is 500 μm, the diameter L1 of thecontact pins 30 is set in the range of 100-50 μm. Thus, the contact pins30 of the IC socket 200 have a significantly smaller diameter than thediameter of the solder bumps 28.

A description will now be given of the operation and function of the ICsocket 200 having the above construction. The IC 25 is mounted on the ICsocket 200 by being fitted inside the cavity 26 of the socket body 21.When the IC 25 is fitted inside the cavity 26, the lid 22 is closed andsecured to the closed position by the lock lever 29. Once the IC 25 ismounted on the IC socket 200, the IC 25 is pressed hard toward thecontact pins 30.

As has been described above, the contact pins 30 are formed of amaterial harder than the material forming the solder bumps 28. Moreover,the diameter L1 of the contact pins 30 is configured to be significantlysmaller than the diameter L2 of the solder bumps 28 such that L1 is⅕-{fraction (1/10)} of L2. Accordingly, the upper ends of the contactpins 30 pierce the solder bumps 28 as the IC 25 is pressed against thecontact pins 30. Consequently, an electrical connection is establishedbetween the contact pins 30 and the solder bumps 28.

The surface of the solder bumps 28 usually has an insulating film (oxidefilm) 34 formed thereon. By the contact pins 30 piercing the insulatingfilm 34, the contact pins 30 can properly establish an electricconnection with the solder bumps 28.

Since the diameter of the contact pins 30 is significantly small asdescribed already, only a small hole is created in the solder bumps 28when the contact pins 30 pierce the solder bumps 38. The solder bumps 28are not substantially deformed to the extent that a variation in theheight of the adjacent solder bumps 28 results. Accordingly, the IC 25can be mounted on the circuit board with high precision after the test.

A description will now be given of specific embodiments of the presentinvention featuring the basic construction described above. FIGS. 7-9show an IC socket 20 according to a first embodiment of the presentinvention. In FIGS. 7-9, those components that correspond to thecomponents of the IC socket 200 shown in FIG. 6 are designated by thesame reference numerals.

As shown in FIGS. 7-9, the IC socket 20 comprises the socket body 21,the lid 22 and a contact unit 23.

The socket body 21 is formed of a molded resin and the cavity 26 isformed inside the socket body 21. The contact unit 23 is designed to befitted in the cavity 26. As shown in FIG. 7-9, the first embodimentfeatures the contact unit 23 which is separate from the socket body 21so that the construction and the constituting material of the contactunit 23 and the socket 21 may be adapted for the respective requiredfunctions.

The cavity 26 is provided with a holding mechanism (not shown) forholding the contact unit 23. The holding mechanism secures the contactunit 23 in the socket body 21. The lid 22 is pivotably fitted to thesocket body 21 by the pivot part 27. When the lid 22 is closed after theIC 25 is mounted on the socket body 21, the lid 22 presses the IC 25toward the contact unit 23.

Accordingly, the solder bumps 28 formed in the IC 25 are pressed towardthe contact unit 23 so that the contact pins 30 constituting the contactunit 23 are electrically connected to the solder bumps 28, as describedlater. The lock lever 29 provided in the lid 22 locks the lid 22 to theclosed position.

The IC socket 20 having the above described construction is mounted onthe test board 32 connected to a test device (for example, a burn-intest device) for testing the IC 25. More specifically, the IC socket 20is mounted on the test board 32 such that the contact unit 23 exposedfrom the underside of the socket body 21 is pressed against the landpart 33 formed in the test board 32, the contact pins 30 are connectedto the land part 33.

A description will now be given of the contact unit 23, the feature ofthe first embodiment. The contact unit 23 comprises the contact pins 30and an elastic member 31 (indicated by a sattin finished texture) forsupporting the contact pins 30.

The contact pins 30 are formed of straight metal wires. Since thecontact pins 30 are straight, the contact pins 30 can be formed bycutting metal wires in a predetermined length. Since such a process doesnot require a die, the cost of production can also be reduced.

The contact pins 30 are formed of a material which is harder than thesolder bumps 28 formed in the IC 25 and which provides a certain springaction described later. For example, the contact pins 30 are formed of atungsten that provides a good spring action or a beryllium copper havinga favorable electrical characteristic.

The diameter (L1) of the contact pins 30 is set to be ⅕-{fraction(1/10)} of the diameter (L2) of the solder bumps 28 (projectionelectrodes) (L1/L2=⅕-{fraction (1/10)}). More specifically, assumingthat the diameter L2 of the solder bumps 28 is 500 μm, the diameter L1of the contact pins 30 is set in the range of 100-50 μm. Thus, thediameter of the contact pins 30 is made to have a significantly smallerdiameter than the solder bumps 28.

The elastic member 31 for supporting the contact pins 30 may be formedof a material capable of elastic deformation such as a foam rubber, afoam glass or a styrene foam. The contact pins 30 are arrayed in theelastic member 31 so as to be aligned with the respective solder bumps28. The contact pins 30 stand embedded in the elastic member 31 suchthat the upper ends thereof are flush with an upper surface 31 a of theelastic member 31. Also, the lower ends of the contact pins 30 are flushwith a lower surface 31 b of the elastic member 31.

By using the elastic member 31 and by supporting the contact pins 30 byembedding the contact pins 30 in the elastic member 31, the contact pins30 are properly supported over the entirety thereof.

A description will now be given, primarily with reference to FIGS. 8 and9, of the operation and function of the IC socket 20 having the abovedescribed construction. In FIGS. 8 and 9, illustration of the socketbody 21 and the lid 22 is omitted.

FIG. 8 shows a state before the IC 25 is mounted on the IC socket 20. Asshown in FIG. 8, the elastic member 31 is not deformed before the IC 25is mounted on the IC socket 20, that is, when the IC 25 is removed fromthe contact unit 23. In this state, the contact pins 30 stand erect bybeing supported by the elastic member 31.

The IC 25 is mounted on the IC socket 20 such that the IC 25 is firstplaced on a predetermined mounting position on the contact unit 23 (atwhich position the solder bumps 28 are aligned with the correspondingcontact pins 30). Subsequently, the lid 22 is closed and the lock lever29 is operated to lock the lid 22 in the closed position. The IC 25mounted on the IC socket 20 is pressed hard toward the contact unit 23.

As described above, the contact pins 30 are formed of a material whichis harder than the material forming the solder bumps 28. The diameter L1of the contact pins 30 is configured to be ⅕-{fraction (1/10)} of thediameter L2 of the solder bumps 28. Accordingly, as the IC 25 is pressedtoward the contact unit 23, upper ends 30 a of the contact pins 30pierce the solder bumps 28 as shown in FIG. 9. Accordingly, the contactpins 30 and the solder bumps 28 are electrically connected to eachother.

The IC socket 20 according to the first embodiment has the followingadded effects compared to the IC socket having the basic construction.

Since the upper ends 30 a of the contact pins 30 are flush with theupper surface 31 a of the elastic member 31, the contact pins 30 piercethe solder bumps 28 so that the solder bumps 28 press the upper surface31 a of the elastic member 31. Since the elastic member 31 iselastically deformable, the elastic member is deformed elastically bybeing pressed by the solder bumps 28. Accordingly, the elastic member 31is prevented from blocking the electrical connection between the contactpins 30 and the solder bumps 28.

Even with their significantly small diameter, the contact pins 30 areprevented from being bent or broken because the contact pins aresupported by the elastic member 31 constituting the contact unit 23.Therefore, the electrical connection with the solder bumps 28 can beproperly established.

A description will now be given of a second embodiment of the presentinvention.

FIGS. 10-12 show an IC socket 20A according to a second embodiment ofthe present invention. In FIGS. 10-12, those components that are thesame as the components of the IC socket 20 according to the firstembodiment described with reference to FIGS. 7-9 are designated by thesame reference numerals, and the description thereof is omitted.

In the IC socket 20 according to the first embodiment, the contact pins30 constituting the contact unit 23 are completely embedded in theelastic member 31 so that only the ends of the contact pins 30 areexposed in the upper surface 31 a and the lower surface 31 b of theelastic member 31. The solder bumps 28 are connected to the contact pins30 such that as the elastic member 31 is elastically deformed by thesolder bumps 28, the contact pins 30 pierce the solder bumps 28.

While the construction of the first embodiment ensures that the contactpins 30 pierce the solder bumps 28, an elastic resilient force producedas the elastic member 31 is elastically deformed acts to remove thesolder bumps 28 away from the contact pins 30. This action also occursin the connection between the elastic member 31 and the test board 32.Thus, the elastic member 31 may obstruct an electric connection betweenthe solder bumps 28 and the contact pins 30, and between the test board32 and the contact pins 30.

An elastic member 31A of the second embodiment has portions thereof inthe vicinity of the ends of the contact pins 30 removed so that theupper ends 30 a and the lower ends 30 b of the contact pins 30 projectfrom the surface of the elastic member 31A. The upper ends 30 a and thelower ends 30 b of the contact pins 30 may be caused to project from therespective surfaces of the elastic member 31A by removing the uppersurface 31 a and the lower surface 31 b of the elastic member 31 to acertain depth or by performing a suitable mechanical or chemicalprocess.

By removing a portion of the upper surface 31 a and the lower surface 31b of the elastic member 31A so that the upper ends 30 a and the lowerends 30 b of the contact pins 30 project from the elastic member 31A,the elastic member 31 is prevented from obstructing a connection betweenthe solder bumps 28 and the contact pins 30 and between the test board32 (the land part 33) and the contact pins 30. Thus, an electricalconnection between the IC 25 and the IC socket 20A and between the ICsocket 20A and the test board 32 can be properly established.

It is not necessary to reduce both the upper surface 31 a and the lowersurface 31 b of the plastic member 31A in the vicinity of the contactpins 30. Only one of the upper surface 31 a and the lower surface 31 bmay be reduced.

Another feature of the IC socket 20A according to the second embodimentis that a positioning plate 36 is provided in the contact unit 23 inaddition to the contact pins 30 and the elastic member 31A. Thepositioning plate 36 is formed of an insulating material such as a glassor a resin like polyimide.

The positioning plate 36 is provided on the upper surface of the elasticmember 31A. The positioning plate 36 is provided with through holes 35that guide the contact pins 30 inserted therein and properly positionsthe contact pins 30. The through holes 35 are aligned with the solderbumps 28 of the IC 25. By inserting the contact pins 30 through thethrough holes 35, the contact pins 30 are positioned so as to be alignedwith the solder bumps 28. The through holes 35 are formed in the blocusing, for example, etching technology because the through holes 35 mustbe aligned with the solder bumps 28 with a high precision.

By providing the positioning plate 36, the contact pins 30 and thesolder bumps 28 can be properly positioned with respect to each otherwhen the IC 25 is mounted on the IC socket 20A.

The background for the second embodiment is that the upper ends 30 a andthe lower ends 30 b of the contact pins 30 may be displaced relativelyfreely if the contact pins 30 are supported only by the elastic member31A so that the contact pins 30 and the solder bumps 28 may not beproperly positioned with respect to each other when the IC 25 is mountedon the IC socket 20A. The positioning plate 26 of the second embodimentensures that the contact pins 30 are properly positioned so that thecontact pins 30 and the solder bumps 28 are properly connected to eachother.

As shown in FIG. 11, an IC positioning part 37 (mounting positioningpart as claimed) for positioning the IC 25 properly is provided in thatpart of the positioning plate 36 where the IC 25 is mounted. The IC 25is properly positioned by its periphery engaging with the IC positioningpart 37. By merely mounting the IC 25 on the IC positioning part 37, theIC 25 can be positioned in the IC socket 20A with a high precision.Accordingly, an electrical connection between the contact pins 30 andthe solder bumps 28 can be properly established.

Positioning recesses 38 (electrode positioning part as claimed) forpositioning the solder bumps 28 are formed on the upper surface of thepositioning plate 36 shown in FIG. 11 so as to be opposite to the solderbumps 28. The positioning recesses 38 are formed to be aligned with thethrough holes 35. The positioning recesses 38 have a conicalconfiguration for proper engagement with corresponding portions of thegenerally spherical solder bumps 28.

When the IC 25 is mounted, the solder bumps 28 are properly positionedby being engaged with the positioning recesses 38. As has beendescribed, since the positioning plate 36 also positions the contactpins 30, the positioning of the contact pins 30 with respect to thesolder bumps 28 is performed with a high precision. Therefore, anelectrical connection between the solder bumps 28 and the contact pins30 can be properly established.

Conical guide recesses 39 for guiding the contact pins 30 insertedtherein are formed on the lower surface of the positioning plate 36 soas to be aligned with the through holes 35. The contact pins 30 areguided by the guide recesses 39 and properly inserted in the throughholes 35. A large number of contact pins 30 can be easily inserted inthe through holes 35 with a relatively small diameter so that themounting process can be performed efficiently.

A plating 40 formed of a conductive material is formed in the innerwalls of the through holes 35 and the guide recesses 39 for properelectrical contact with the contact pins 30. The plating 40 is alsoformed in the positioning recesses 38 for proper electrical contact withthe solder bumps 28. Accordingly, the plating 40 serves to establish anelectrical connection between the contact pins 30 and the solder bumps28.

More specifically, the contact pins 30 come into contact with theplating 40 and are electrically connected therewith when inserted intothe through holes 35. Since the plating 40 is also formed in thepositioning recesses 38 which come into contact with the solder bumps28, the plating 40 is electrically connected to the solder bumps 28.Accordingly, the effective contact surface between the contact pins 30and the solder bumps 28 increases so that an electrical connectionbetween the contact pins 30 and the solder bumps 28 can be more properlyestablished.

A description will now be given of an alternative construction whichensures a proper connection between the contact pins 30 and the solderbumps 28.

In the construction shown in FIG. 13A, an insulating member 51 providedwith an IC positioning part 52 for positioning the IC 25 is formed inthe elastic member 31 for supporting the contact pins 30. The insulatingmember 51 is formed of a resin (for example, a polyimide resin or thelike) providing an electrical insulation. The IC positioning part 52formed in the insulating member 51 is a rectangular opening in which theIC 25 is mounted.

By mounting the IC 25 on the IC positioning part 52, the IC 25 can beproperly positioned with respect to the elastic member 31. Therefore, anelectrical connection between the contact pins 30 and the solder bumps28 formed in the IC 25 can be properly established.

In the construction shown in FIG. 13B, the elastic member 31 is providedwith an insulating member 51A in which a bump positioning part 53 isformed to accommodate the solder bumps 28 formed in the IC 25. Bypositioning the solder bumps 28 formed in the IC 25 so as to be fittedin the bump positioning part 53, the solder bumps 28 can be properlypositioned with respect to the elastic member 31. Therefore, anelectrical connection between the contact pins 30 and the solder bumps28 can be properly established.

In the construction shown in FIG. 14A, an IC positioning part 52A forproperly positioning the IC 25 is formed to be integral with the elasticmember 31. The IC positioning part 52A may be formed by providing, onthe elastic member 31, a mask 54 having an opening aligned with the ICmounting position so that a portion of the elastic member 31 is removedusing chemical etching. While the mask 54 is shown in FIG. 14A, it is tobe removed before the IC 25 is mounted on the IC positioning part 52A.

Like the construction shown in FIG. 13A, the construction shown in FIG.18A also ensures that the IC 25 can be properly positioned with respectto the elastic member 31 just by mounting the IC 25 on the ICpositioning part 52A. Therefore, an electrical connection between thecontact pins 30 provided in the elastic member 31 and the solder bumpsformed in the IC 25 can be properly established. Since the ICpositioning part 52A is formed to be integral with the elastic member31, the IC 25 can be positioned using a simple construction.

In the construction shown in FIG. 14B, a bump positioning part 53A forpositioning the bumps 28 is formed to be integral with the elasticmember 31. By mounting the solder bumps 28 formed in the IC 25 on thebump positioning part 53A, an electrical connection between the contactpins 30 and the solder bumps 28 can be properly established. Since thebump positioning part 53A is formed to be integral with the elasticmember 31, the solder bumps 28 can be positioned using a simpleconstruction.

A description will now be given of a third embodiment of the presentinvention.

FIG. 15 shows a portion of an IC socket 20B according to a thirdembodiment of the present invention. Illustration of the socket body 21and the lid 22 is omitted. In FIG. 15, those components that are thesame as the components of the IC socket 20 and 20A according to thefirst and second embodiments, respectively, are designated by the samereference numerals and the description thereof is omitted.

The IC socket 20B according to the third embodiment is constructed suchthat an upper guide plate 41 and a lower guide plate 42 are provided ina contact unit 23B to sandwich the elastic member 31A provided with thecontact pins 30. The upper guide plate 41 and the lower guide plate 42are provided with positioning holes 43 an 44, respectively, forpositioning the contact pins 30. The contact pins 30 are movably guidedby the positioning holes 43 and 44.

In order to prevent a relative displacement (dislocation) of the upperguide plate 41 and the lower guide plate 42, a dislocation preventingplate 45 is provided at the sides of the upper guide plate 41 and thelower guide plate 42. The upper end of the dislocation preventing plate45 is fixed to the upper guide plate 41 and the lower end of thedislocation preventing plate 45 is fixed to the lower guide plate 42.Accordingly, a dislocation of the upper guide plate 41 and the lowerguide plate 42 is prevented.

The third embodiment shows that the contact unit may have a pair ofguide plates provided to sandwich the elastic member 31A instead of thepositioning plate of the second embodiment provided on the upper surfaceof the elastic member 31A or instead of an alternative guide plateprovided on the lower surface thereof. According to the construction ofthe third embodiment, the contact pins 30 are positioned at the upperand lower ends thereof so that an electrical connection between thesolder bumps 28 and the contact pins 30 and between the test board 32(the land part 33) and the contact pins 30 can be properly established.

FIG. 16 is a bottom view of the lower guide plate 42 provided on thelower surface of the elastic member 31A. As shown in FIG. 16, connectionparts 46, land parts 47 and lead parts 48 are printed on that surface ofthe lower guide plate 42 that faces the test board 32. The connectionparts 46 are electrically connected to the contact pins 30. For example,the connection parts 46 may be through hole electrodes formed in thepositioning holes 44. Therefore, the connection parts 46 are provided atthe same pitch as the pitch of the contact pins 30 (and the pitch of thesolder bumps 28).

The land parts 47 may be formed at a pitch wider than the pitch of theconnection parts 46 because the arrangement of the land parts 47 is notdetermined by the arrangement of the contact pins 30. The lead parts 48electrically connect the connection parts 46 and the land parts 47.

Since the arrangement of the connection parts 46 is determined by thearrangement of the contact pins 30, the pitch of the connection parts 46can not be enlarged. However, the lead parts 48 according to the thirdembodiment for leading the connection parts 46 to the land parts 47ensures that the pitch of the connection parts 46 is virtually enlargedso as to be equal to the pitch of the land parts 47.

Accordingly, as shown in FIG. 8, by providing the land parts 47 withexternal connection terminals 49 for connection with the test board 32,an electrical connection between the test board 32 and the IC socket 20Bcan be easily and properly established.

A description will now be given of a fourth embodiment of the presentinvention.

FIGS. 17 and 18 are schematic views of an IC socket 20C according to thefourth embodiment. Illustration of the socket body 21 and the lid 22 isomitted. In FIGS. 17 and 18, those components that are identical to thecomponents of the IC socket 20B according to the third embodiment shownin FIG. 15 are designated by the same reference numerals and thedescription thereof is omitted.

The feature of the IC socket 20C according to the third embodiment isthat the contact pins 30 provided in a contact unit 23C are fixed to theupper guide plate 41 such that their heights from the surface of theguide plate 41 are uniform. Referring to FIG. 17, the contact pins 30are made to have the regular height H from the surface of the upperguide plate 41. The contact pins 30 may be fixed to the upper guideplate 41 using, for example, an adhesive 50. By using the adhesive 50,the contact pins 30 and the upper guide plate 41 become integral witheach other. The contact pins 30 are not fixed to the lower guide plate42 provided on the lower surface of the elastic member 31A. Theconstruction involving the contact pins 30 and the lower guide plate 42are the same as the corresponding construction according to the thirdembodiment.

As described above, by fixing the contact pins 30 to the upper guideplate 41, a variation in the height of the upper ends 30 a of thecontact pins 30 connected to the solder bumps 28 can be prevented.

A case is assumed in which the contact pins 30 are movable with respectto the upper guide plate 41 (that is, assuming the construction of thethird embodiment), and in which the test board 23 is warped as shown inFIGS. 17 and 18. As described in the foregoing embodiments, since thelower ends 30 b of the contact pins 30 come into contact with the testboard 32 and are electrically connected thereto, a variation in theheight of the upper ends 30 a of the contact pins 30 conforming to theconfiguration of the test board 32 occurs.

If a variation in the height of the upper ends 30 a of the contact pins30 occurs, the depth of the contact pins 30 piercing the solder bumps 28differs from pin to pin. Accordingly, a variation in the conductivityoccurs and the test may not be successfully conducted.

By fixing the contact pins 30 to the upper guide plate 41 in a uniformheight from the surface of the upper guide plate 41 according to thefourth embodiment, the upper ends 30 a of the contact pins 30 aremaintained at the uniform height H from the upper guide plate 41 evenwhen the test board 32 does not have a level surface due to a warp orthe like. Therefore, as shown in FIG. 18, the contact pins 30 pierce thesolder bumps 28 to the regular depth so that the electrical conductivitybetween the contact pins 30 and the solder bumps 28 is stabilized.

The contact pins 30 are inserted through the positioning holes 44 of thelower guide plate 42 so as to be displaceable therein. The contact pins30 and the elastic member 31A supporting the contact pins 30 areelastically deformable. For this reason, even when the test board 32 hasa rugged surface due to a warp or the like, the contact pins 30 and theelastic member 31A are elastically deformed below the upper guide plate41. Accordingly, the contact pins 30 can be properly connected to theland parts 33 formed on the test board 32 when the contact pins 30 arefixed to the upper guide plate 41 at the prescribed positions thereof.

The depth to which the contact pins 30 pierce the solder bumps 28 isdetermined by the height H of the contact pins 30 projecting above theupper guide plate 41. That is, when the solder bumps 28 come intocontact with the upper guide plate 41, the contact pins 30 do notpenetrate the solder bumps 28 further. In this way, it is possible toprevent the contact pins 30 from piercing the solder bumps 28 beyond arequired depth. Thus, the solder bumps 28 are prevented from beingdamaged and the main body of the IC 25 is prevented from being damagedby the contact pins 30 piercing the solder bumps 28.

While it is assumed that only the contact unit 23C is provided in the ICsocket 20C of the fourth embodiment described with reference to FIGS. 17and 18, it is also possible to provide the positioning plate 36described with reference to FIGS. 10 and 11 in the IC socket 20C. Abenefit added to the fourth embodiment by providing the positioningplate 36 is that the IC 25 can be positioned with a higher precision andthe solder bumps 28 and the contact pins 30 are electrically connectedto each other more properly.

A description will now be given of an IC socket according to a fifthembodiment.

FIG. 19 shows an IC socket 20D according to a fifth embodiment. In FIG.15, those components that are identical to the components of the ICsocket 20B according to the third embodiment described with reference toFIG. 15 are designated by the same reference numerals and thedescription will be omitted.

The IC socket 20D according to the fifth embodiment differs from the ICsocket 20B according to the third embodiment shown in FIG. 15 in thatthe elastic member 31A and the dislocation preventing plate 45 areeliminated and the upper guide plate 41 and the lower guide plate 42 forsupporting the contact pins 30 are provided.

The upper guide plate 41 is provided with supporting holes 56 in whichthe contact pins 30 are inserted and adhesively fixed, and the lowerguide plate 42 is provided with supporting holes 57 in which the contactpins 30 are inserted. The upper guide plate 41 and the lower guide plate42 are spaced apart so as to reside near the upper ends and the lowerends of the contact pins 30, respectively.

Therefore, only the contact pins 30 exist between the upper guide plate41 and the lower guide plate 42. The contact pins 30 according to thefifth embodiment are not supported by the elastic member and are moreeasily displaced between the upper guide plate 41 and the lower guideplate 42 than the contact pins 30 of the foregoing embodiments.

Assuming that the contact pins 30 are supported in such a manner that itis impossible or difficult for the contact pins 30 to be displaceable, avariation in the electrical connection between the the contact pins 30and the test board 32, and between the contact pins 30 and the solderbumps 28 occurs if the height of the solder bumps 28 formed on the IC 25differs from bump to bump, or if the test board 32 does not have a levelsurface due to a warp or the like. If there is a variation in theelectrical connection, an associated variation in the electricalconductivity occurs and the test may not be conducted properly.

In the IC socket 20D according to the fifth embodiment, since thecontact pins 30 are easily displaceable between the upper guide plate 41and the lower guide plate 42, the elastic deformation of the contactpins 30 cancels the variation in the height of the solder bumps 28 andthe warp or the like of the test board 32. Accordingly, a properelectrical connection is established between the contact pins 30 and thesolder bumps 28, and between the contact pins 30 and the test board 32,resulting in a stabilized electrical conductivity.

A description will now be given, with reference to FIGS. 20A-23C, ofconfigurations of the ends of the contact pins 30 connected to thesolder bumps 28 and the land parts 33 of the test board 32.

In the construction shown in FIGS. 20A and 20B, at least the ends of thecontact pins 30 piercing the solder bumps 28 are formed as a sharp edge.FIG. 20A shows a conical sharp edge 60 provided at the end of thecontact pin 30. FIG. 20B shows a diagonally cut sharp edge 61 at the endof the contact pin 30.

The conical sharp edge 60 and the diagonally cut sharp edge 61 may beformed by grinding, chemically treating or diagonally cutting the end ofthe contact pin 30 exposed from the elastic member. By forming the sharpedges 60 or the sharp edges 61 in the contact pins 30, it is easy forthe contact pins 30 to pierce the solder bumps 28 and the damage causedin the solder bumps 28 can be reduced (the solder bumps 28 are deformedto a smaller degree).

In the construction shown in FIG. 20C, the contact pins 30 are providedwith a plating 62 at its end. The plating 62 may be formed of gold (Au)or the like characterized by a good conductivity. By forming the plating62 at the end of the contact pins 30, an electrical conductivity betweenthe contact pins 30 and the solder bumps 28 pierced thereby can beimproved.

While the contact pins 30 are configured to pierce the solder bumps 28according to the foregoing embodiments, the contact pins 30 shown inFIGS. 21C-23C are configured to establish an electrical connection withthe solder bumps 28 without piercing the solder bumps 28.

The construction shown in FIGS. 21A and 21B features a spiral part 63formed at the end of the contact pins 30. The spiral part 63 isinherently displaceable in a longitudinal direction.

As shown in FIG. 21B, when the IC is mounted so that the solder bumps 28formed thereon contact the spiral part 63, the solder bumps 28,characteristically formed of a soft material, are prevented from beingdamaged or deformed thanks to an elastic deformation of the spiral part63. Further, the spiral part 63 comes into contact with the solder bump28 at positions indicated by the circles drawn by the broken lines inFIG. 21B, which positions are removed from the lower end of the solderbump 28.

Since the lower end of the solder bump 28 is soldered to the board towhich the IC 25 is mounted, any damage or deformation in the lower endmay prevent the mounting process from being performed properly. Byforming the spiral part 63 at the end of the contact pins 30 so that thecontact pins 30 do not come into contact the lower end of the solderbumps 28, the lower end of the solder bumps 28 is prevented from beingdamaged or deformed when the IC is tested.

In the construction shown in FIG. 22A, a randomly deformed part 64 isformed at the end of the contact pins 30 by bending the end in a randommanner. By providing the randomly deformed part 64 at the end of thecontact pins 30, the solder bumps 28 are encased in the randomlydeformed part 64 and remain in contact therewith while the IC is beingtested. The solder bumps 28, characteristically formed of a softmaterial, are prevented from being damaged or deformed, and anelectrical connection therewith can be properly established.

In the construction shown in FIG. 22B, a coil part 65 is produced at theend of the contact pins 30 so that the longitudinal direction of thecoil part 65 is perpendicular to the longitudinal direction of thecontact pins 30. By forming the coil part 65 at the end of the contactpins 30, the coil part 65 is deformed according to the configuration ofthe solder bumps 28 when the solder bumps 28 are pressed against thecoil part 65 in testing the IC. Accordingly, the solder bumps 28 comeinto contact with the coil part 65 at a large number of points.Accordingly, an electrical connection between the solder bumps 28 andthe contact pins 30 can be properly established.

Any variation in the height of the solder bumps 28 or the irregularityon the surface of the test board 32 can be canceled by a deformation ofthe coil part 65. In this way, an electrical conductivity between thesolder bumps 28 and the contact pins 30 can be improved.

In the construction shown in FIG. 23A, an arcuate part 66 is provided atthe end of the contact pins 30 by bending it into an arcuateconfiguration. The arcuate part 66 provides a spring action.

When the solder bump 28 presses the arcuate part 66 while the IC isbeing tested, the arcuate part 66 is deformed as illustrated in FIG.23A. Therefore, the force (exercised as a counter force of a pressureprovided by the lid 22 on the IC 25) against the solder bumps 28 can berelieved. Accordingly, the solder bumps 28 can be prevented from beingdamaged or deformed. Any variation in the height of the solder bumps 28and the irregularity on the surface of the test board 23 can becanceled.

In the construction shown in FIG. 23B, the end of the contact pin 30 isbent to form a crooked part 67. The crooked part 67 formed at the end ofthe contact pins 30 provides the same function as the arcuate part 66shown in FIG. 23A. Accordingly, the solder bumps 28 can be preventedfrom being damaged or deformed. Any variation in the height of thesolder bumps 28 and the irregularity on the surface of the test board 23can be canceled by the crooked part 67.

As has been described, by forming the spiral part 63, the randomlydeformed part 64, the coil part 65, the arcuate part 66 or the crookedpart 67 at that portion of the contact pins 30 connected with the solderbump 28 so that any of these parts comes into contact with the solderbump 28 and is deformed accordingly, any variation in the height of thesolder bumps 28 and the irregularity on the surface of the test board 23can be canceled. Since the parts 63-67 are deformed according to theconfiguration of the solder bump 28, a relatively wide contact area issecured. Accordingly, an electrical conductivity between the contactpins 30 and the solder bumps 28 can be improved.

Also, even if the material forming the solder bumps 28 is soft, thecontact pins 30 and the solder bumps 28 can be electrically connected toeach other without any damage being caused in the solder bumps 28because the parts 63-67 are formed to be deformable.

In the construction shown in FIG. 23C, the contact pin 30 is providedwith a sharply-bent part 68 provided by bending the end of the contactpin 30 piercing the solder bump 28 in a sharp angle.

The sharply bent part 68 formed at the end of the contact pin 30 is bentin an even sharper angle when the contact pin 30 pierce the solder bump28 (that is, the sharply bent part 68 is deformed from the stateindicated by the broken line of FIG. 23C to the state indicated by thesolid line). The sharply bent part 68 that has pierced the solder-bump28 and is located therein presses the solder bump toward the peripheryof the solder bump 28, due to an elastic resilient force. Accordingly,an electrical connection between the contact pins 30 and the solderbumps 28 can be properly established.

A description will now be given of the mounting mechanism for mountingthe IC sockets 20, 20A-20D on the test board 32.

FIGS. 24A-24C shows variations of the mounting mechanism. The mountingmechanisms shown in FIGS. 24A-24C have the same basic construction. Inthe construction shown in FIG. 24A, an elastically deformable part 71 isformed at that end of the contact pin 30 which is connected to the testboard 23. In the construction shown in FIG. 24B, an elasticallydeformable part 72 is formed at that end of the contact pin 30 which isconnected to the test board 23. In the construction shown in FIG. 24C,an elastically deformable part 73 is formed at that end of the contactpin 30 which is connected to the test board 23. The contact pin 30 ispressed against a through hole 70 formed in the test board 32 due to anelastic resilient force generated when the elastically deformable part71 (72, 73) is inserted, so that an electrical connection is properlyestablished between the elastically deformable part 71 (72, 73) and thethrough hole 70.

More specifically, the elastically deformable part 71 shown in FIG. 24Ais in the form of a sharp edged bend 71; the elastically deformable part72 shown in FIG. 24B is in the form of a curve; and the elasticallydeformable part 73 shown in FIG. 24C is in the form of a coil.

The elastically deformable part 71 (72, 73) is fitted in the throughhole 70 by first deforming them so that it is elongated in thelongitudinal direction and inserting it in the through hole 70 while theelongated state is maintained. Subsequently, the elastically deformablepart is relieved of the force applied to cause the elongateddeformation. Thus, the elastically deformable part 71 (72, 73) returnsto an original configuration due to an elastic resiliency inside thethrough hole 70. Due to this elastic resilient force, the elasticallydeformable part 71 (72, 73) presses itself against the inner wall of thethrough hole 70 and establishes an electrical connection therewith.

According to the above-described mounting mechanism for mounting the ICsocket 20, 20A-20D on the test board 32, an electrical connectionbetween the contact pins 30 and the test board 32 can be properlyestablished by a simple operation of inserting the elasticallydeformable parts 71 (72, 73) into the through hole 70. Since theelastically deformable part 71 (72, 73) presses the through hole 70 byan elastic resilient force while the electrical connection isestablished, an electrical conductivity between the contact pins 30 andthe test board 32 can be improved.

In the mounting mechanism shown in FIGS. 25A and 25B, the through holes70 are formed at a pitch P2 wider than the pitch P1 at which the solderbumps 28 and the contact pins 30 are provided (P1<P2). As shown in FIG.25A, the foot of the contact pins 30 projecting toward the test board 32through the elastic member 31 supporting the contact pins 30 areconfigured to be long enough to reach the respective through holes 70.

As shown in FIG. 25B, the contact pins 30 are electrically connected tothe test board 32 such that the portions of the contact pins 30projecting through the elastic member 31 are guided into the respectivethrough holes 70 and connected thereto.

According to the mounting mechanism of FIGS. 25A and 25B, the pitch P2of the through holes 70 is wider than the pitch P1 of the solder bumpswhich may be relatively narrow. Therefore, forming of the through holes70 becomes easier, and forming of the wiring pattern (not shown)provided on the test board 32 for connection with the through holes 70also becomes easier.

The present invention is not limited to the above-described embodiments,and variations and modifications may be made without departing from thescope of the present invention.

What is claimed is:
 1. An IC socket mounted on a test board while in use and having a semiconductor device with projection electrodes comprising respective generally spherical portions and mounted on said IC socket for testing, said IC socket comprising: a plurality of straight contact pins each including a first end electrically connected to said test board and a second end connected to the respective generally spherical portions of said projection electrodes; and a supporting structure for supporting said plurality of contact pins, each of said plurality of contact pins provided at the second end with a substantially spiral portion subject to an elastic deformation by a pressure occurring between said contact pin and an associated generally spherical portion of one of said projection electrodes, wherein each of said plurality of contact pins has a sufficiently small diameter such that said contact pin is fitted to the associated generally spherical portion of one of said projection electrodes by the deformation, and wherein a lower end of the associated generally spherical portion is not contacted by the spiral portion, whereby the lower end is not damaged by the contact pin.
 2. The IC socket as claimed in claim 1, wherein the second end of each contact pin is in contact with said projection electrodes.
 3. The IC socket as claimed in claim 1, wherein the substantially spiral portion decreases in diameter from the second end toward a straight portion of the contact pin.
 4. An IC socket mounted on a test board while in use and having a semiconductor device with projection electrodes mounted on said IC socket for testing, said IC socket comprising: a plurality of straight contact pins having a first end electrically connected to said test board and a second end connected to said projection electrodes; and a supporting structure for supporting said plurality of contact pins, each of said plurality of contact pins provided at the second end with a non-straight portion subject to an elastic deformation by a pressure occurring between said contact pin and an associated one of said projection electrodes; wherein a supporting structure is provided separate from a main body of said IC socket, said supporting structure is provided by an elastic member so that said plurality of contact pins are inserted into said elastic member and supported therein.
 5. An IC test system for testing a semiconductor device with projection electrodes comprising respective generally spherical portions and mounted on an IC socket which is mounted on a test board connected to a test device, said IC socket comprising: a plurality of straight contact pins each including a first end electrically connected to said test board and a second end connected to the respective generally spherical portions of said projection electrodes; and a supporting structure for supporting said plurality of contact pins, each of said plurality of contact pins provided at the second end with a substantially spiral portion subject to an elastic deformation by a pressure occurring between said contact pin and an associated generally spherical portion of one of said projection electrodes, and wherein a lower end of the associated generally spherical portion is not contacted by the spiral portion, whereby the lower end is not damaged by the contact pin.
 6. The IC socket as claimed in claim 5, wherein the second end of each contact pin is in contact with said projection electrodes.
 7. The IC socket according to claim 1, wherein the diameter of the contact pins is ⅕-{fraction (1/10)} of a diameter of the projection electrodes.
 8. The IC test system according to claim 5, wherein the diameter of the contact pins is ⅕-{fraction (1/10)} of a diameter of the projection electrodes. 